The principal source of energy for warming streams is the sun. The amount of sunlight reaching the stream may be increased after clear‐cut logging. Average monthly maximum temperatures increased by 14°F and annual maximum temperatures increased from 57° to 85°F one year after clear‐cut logging on a small watershed in Oregon's coast range. In a nearby watershed where strips of brush and trees separated logging units from the stream, no changes in temperature were observed that could be attributed to clear‐ cutting.